In general, a construction machine such as a wheel loader or an excavator cools a radiator and an oil cooler placed in front thereof by forcibly sucking outdoor air through a cooling fan. However, in the case in which a hydraulic motor driving the cooling fan rotates (positively rotates) only in one direction at all times, dust is attached to the radiator and the like, thus, causing an inconvenience to an operator due to requiring periodic cleaning. Therefore, in recent years, a device has been used, which reversibly rotates the cooling fan by switching a rotation direction of the hydraulic motor through a switching valve to blow away dust accumulated by the blowing of the cooling fan.
In this connection, Korea Patent No. 840044 owned by an applicant discloses a driving control device of a cooling fan of construction heavy equipment. The disclosed driving control device includes a hydraulic pump, a hydraulic motor driven by pressure oil supplied from the hydraulic pump through a hydraulic line, and a cooling fan driven by the hydraulic motor. The hydraulic motor is configured by a hydraulic motor that rotates positively or reversibly. A switching valve that changes a supplying direction of the pressure oil and a switch electrically controlling the switching valve are provided on the hydraulic line connected from the hydraulic pump to the hydraulic motor.
In the related art, in general, a single cooling fan is adopted. However, in the case in which a plurality of cooling fans are provided in order to improve cooling efficiency, a plurality of switching valves need to be provided so as to change a rotation direction of each of the cooling fans, and as a result, the device becomes complicated and layout efficiency of parts deteriorates.
Further, when the cooling fan stops instantly in order for the cooling fan rotating positively or reversibly to change its rotation direction to the opposite direction or stop its operation by the switching valve, a sharp pressure drop region, i.e., a “cavity” is generated in the rear of the hydraulic motor, i.e., a point where the pressure oil is inputted into the hydraulic motor on the basis of a flowing direction of the pressure oil due to inertia. The cavity causes a large pressure difference in a mechanism, thereby deteriorating the performance of the hydraulic motor.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.